IP Library Granted Patent US 7,602,375
Granted Patent B2
US 7,602,375 · App. 11/100,762 · Granted Oct 13, 2009

Method and system for writing data to MEMS display elements

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Quick Facts
Patent No.
US 7,602,375
App. No.
11/100,762
Granted
Oct 13, 2009
Kind
B2
Abstract

Charge balanced display data writing methods use write and hold cycles of opposite polarity during selected frame update periods. A release cycle may be provided to reduce the chance that a given display element will become stuck in an actuated state.

Claims (30)

1. A method of actuating a MEMS display element, said MEMS display element comprising a portion of an array of MEMS display elements, said method comprising:

writing display data to said MEMS display element with a potential difference of a first polarity during a first portion of a display write process;

re-writing said display data to said MEMS display element with a potential difference having a polarity opposite said first polarity during a second portion of said display write process;

applying a first bias potential having said first polarity to said MEMS display element during a third portion of said display write process; and

applying a second bias potential having said opposite polarity to said MEMS display element during a fourth portion of said display write process,

wherein a state of said MEMS display element does not change during said third and fourth portions.

2. The method of claim 1 , wherein said first portion of said display write process comprises writing a first frame of display data to said array of MEMS display elements, and wherein said second portion of said display write process comprises re-writing said first frame of display data to said array of MEMS display elements.

3. The method of claim 2 , wherein said third and fourth portions of said display write process comprises holding said first frame of display data following said re-writing.

4. The method of claim 3 , additionally comprising writing a second frame of display data using said writing, re-writing, applying a first bias potential and applying a second bias potential.

5. The method of claim 1 , wherein said first portion of said display write process comprises writing a first row of display data to said array of MEMS display elements, and wherein said second portion of said display write process comprises re-writing said first row of display data to said array of MEMS display elements.

6. The method of claim 5 , wherein said third and fourth portions of said display write process comprises holding said first row of display data following said re-writing.

7. The method of claim 6 , additionally comprising writing a second row of display data using said writing, re-writing, applying a first bias potential and applying a second bias potential.

8. The method of claim 1 , wherein said first, second, third, and fourth portions of said display write process each comprise approximately one-fourth of a time period defined by the inverse of a rate at which frames of display data are received by a display system.

9. The method of claim 1 , wherein said first portion and said second portion together comprise less than ½ of a time period defined by the inverse of a rate at which frames of display data are received by a display system.

10. The method of claim 1 , wherein said first portion extends for a first time period and said second portion extends for a second time period.

11. The method of claim 10 , wherein said first and second time periods are different.

12. The method of claim 11 , wherein said first and second time periods are determined based at least in part on a polarity dependent dielectric charging rate.

13. A method of maintaining a frame of display data on an array of MEMS display elements, said method comprising alternately applying approximately equal bias voltages of opposite polarities to each of said MEMS display elements for periods of time defined at least in part by the inverse of a rate at which frames of display data are received by a display system.

14. The method of claim 13 , wherein each said period of time is substantially equal to 1/(2f), wherein f is a defined frequency of frame refresh cycles.

15. The method of claim 13 , wherein each said period of time is substantially equal to 1/(4f), wherein f is a defined frequency of frame refresh cycles.

16. A method of writing frames of display data to an array of MEMS display elements at a rate of one frame per defined frame update period, said method comprising:

writing display data to said MEMS display elements, wherein said writing takes less than said frame update period; and

applying a series of bias potentials of alternating polarity to said MEMS display elements for the remainder of said frame update period,

wherein a state of said MEMS display elements does not change during said remainder.

17. The method of claim 16 wherein said series comprises an application of a first polarity during approximately half of said remainder of said frame update period, and an application of a second opposite polarity during approximately half of said frame update period.

18. A MEMS display device configured to display images at a frame update rate, said frame update rate defining a frame update period, said display device comprising a column driver circuit configured to apply a polarity balanced sequence of bias voltages to substantially all columns of a MEMS display array for portions of at least one frame update period, wherein a state of said MEMS display array does not change during said portions, and wherein said portions are defined by a time remaining between completing a frame write process for a first frame, and beginning a frame write process for a next subsequent frame.

19. The MEMS display device of claim 18 , wherein said driver circuit is configured to apply the same voltage to substantially all columns of said display array during a portion of said frame update period.

20. A method of driving a MEMS display comprising periodically releasing substantially all pixels of said display, wherein said periodic releasing occurs for each pixel at an infrequent rate such that there is no perceptible effect on visual appearance of the display to a normal observer.

21. The method of claim 20 , wherein any given periodically released pixel is released at a rate slower than once per hour of display use.

22. The method of claim 20 , wherein any given periodically released pixel is released at a rate slower than once per 100,000 displayed frames of image data.

Assignments (3)
ASSIGNMENT OF ASSIGNOR'S INTEREST Recorded Aug 31, 2016
From: QUALCOMM MEMS TECHNOLOGIES, INC.
To: SNAPTRACK, INC.
Reel/Frame 039891/0001 →
ASSIGNMENT OF ASSIGNOR'S INTEREST Recorded Oct 28, 2009
From: IDC, LLC
To: QUALCOMM MEMS TECHNOLOGIES, INC.
Reel/Frame 023435/0918 →
ASSIGNMENT OF ASSIGNOR'S INTEREST Recorded Apr 6, 2005
From: CHUI, CLARENCE; KOTHARI, MANISH
To: IDC, LLC
Reel/Frame 016454/0903 →